After World War Two ended, there were still lots of people who were not where they wanted to be, where they were supposed to be or were in a situation where they would still be killed in short order if they did not move.

Warfare causes more than just physical wounds – but the mental side of the toll of war was really not studied for centuries (mainly because common soldiers were expendable anyway). So the study really started only around the World War One. Ben Shephard traces some of those developments, mostly based of Western European and US records. ( From shell shock to PTSD )